The present invention relates to a data recording disk, and more particularly to a data recording disk which is made more resistant to burst errors without decreasing recording capacity.
In a data recording disk, a track of one rotation's portion is normally divided into a plurality of sectors. Further, it is arranged so that address information is recorded in each sector, and predetermined data are recorded and regenerated in each sector with the address as reference.
In order to make access to a data recording disk quickly, it is desirable to rotate the disk at a constant angular velocity (CAV). When a disk is rotated at a constant angular velocity, however, linear recording density along the outer circumference of the disk becomes lower than that along the inner circumference thereof, and the recording capacity becomes smaller by that portion.
Now, a disk that is made to be driven at a constant linear velocity (CLV) is also known. When the CLV is adopted, linear recording densities along the inner circumference and the outer circumference of the disk become equal to each other. Therefore, it is possible to increase the recording capacity of the disk by that portion. In the CLV disk, however, access performance is deteriorated since the position of the sector in each track varies from track to track.
Accordingly, a zone CAV disk in which the track is divided radially into a plurality of zones and the number of the sectors per track in an outside zone is set so as to be made larger by one sector more than the number of sectors per track in an inside zone successively, and which is rotated at a constant angular velocity has been proposed. Within the zone, the number of sectors per track is made constant. Accordingly, although the recording density is not as high as the CLV disk, it is possible to improve the recording density as compared with the CAV disk. Further, since the zone CAV disk is always rotated at a constant rotational angular velocity (namely, since it is similar to a normal CAV disk in this point), irrespective of the zone, quick access becomes possible as compared with the CLV disk.
Now, it is desired of late to further increase the recording capacity of the data recording disk. As a result, such a tendency that a track pitch is narrowed and a bit length is shortened, thereby to make a surface density of the whole disk higher is being developed. For example, such values that 0.9 .mu.m as the track pitch and 0.34 .mu.m as the bit length are proposed.
When recording at high density is performed by making the track pitch and the bit length shorter, the length of one sector becomes shorter. As a result, in such a case that a disk is injured in a predetermined length, the number of data that are damaged within a sector for a crack in the same length is increased as densification is advanced.
Since detection and correction of errors in data are normally made in the unit of sector, it means that, when densification advances, the disk becomes weaker against burst errors by that portion.
Therefore, it is conceivable to increase the interleaving length in order to make the disk stronger against burst errors. In order to increase the interleaving length, it is required to make the sector length longer for instance. However, there has been a subject that, when a longer sector is adopted, zoning efficiency is deteriorated and the recording capacity of the disk is reduced.
Therefore, as shown in FIG. 19 for instance, a scope for error detection and correction (a scope of interleaving) is set extending over several sectors in a CLV disk for a ROM for exclusive use for regeneration.
In the example shown in FIG. 19, one sector is composed of 28 frames, one frame is consisted of 87 bytes, and a frame sink (FS) in two bytes is added to each frame.
Further, 20 bytes at the head of each sector are used as an address area, where sector addresses are arranged.
Further, a C1 code and a C2 code are used as error correction codes, and the C1 codes are provided for those data that are arranged in a horizontal direction in the figure and the C2 codes are provided for those data that are arranged in an oblique direction. The C1 code is to consist of 8 bytes and the C2 code of 14 bytes.
Besides, an error detection code (EDC) in 4 bytes is also provided in each sector.
Namely, in this example, the interleaving length of the C1 code becomes 170 bytes, and the interleaving length of the C2 code is to include 170 bytes (170 frames).
In this example, however, since the error correction on the address is made similarly to the error correction on the data, the data of 170 frames (approximately 13 sectors) have to be read in order to make error detection and correction of the addresses, and quick error detection and correction cannot be made, thus causing a subject of preventing quick access.